Permeability properties of fine recycled aggregate concrete Lus - - PowerPoint PPT Presentation

Permeability properties of fine recycled aggregate concrete

Luís Evangelista1,3, Jorge de Brito1,4

1 University of Stavanger, Norway 2 Instituto Superior Técnico, Portugal 3 CERIS – ICIST, Instituto Superior Técnico, Portigal

• 1. INTRODUCTION
• 2. STATE-OF-THE-ART
• 2. EXPERIMENTAL PROGRAM
• 3. POROSITY OF FRAC

3.1. Water absorption by immersion 3.2. Capillary water absorption 3.3. Carbonation 3.4. Chloride penetration resistance 3.5. Electrical resistivity

• 4. CONCLUDING REMARKS

TABLE OF CONTENTS

INTRODUCTION

World population growth and mass exodus to urban areas keeps the construction industry ever increasing. It is estimated that 10 billion of m3 of concreet are produced each year. The natural aggregates consumption is between 17 and 37 x103 Mt/year EUA: 130 Mt/y EU: 380 - 850 Mt/y China: 325 - 345 Mt/y By the year 2020, 70% of CDW roduced in EU has to be reintroduced in the industrial cycle.

INTRODUCTION

One way of solving both problems is by using recycled aggregates in concrete production. Currently, the trend is

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CRA AFR FRA have very high water absorption and high levels of contaminant particles.

Research objective

To evaluate the performance of FRAC made with different replacement ratios, so that the existing trend may change in the near future

• Initial studies on FRAC showed that the environmental

benefits were outweighted by the poorest performance.

• As a result, the existing standards ban or strongly limit

the use of FRA in concrete production

• From the beginning of the XXI century, new studies seem to contradict the

common knowledge that the use of FRA is very harmful to concrete performance, if FRA are treated as they should.

• Durability wise, FRAC show considerably poorer behavior than conventional
• concrete. Some previous results showed performance losses above 100%, due

to the higher porosity of FRA.

STATE-OF-THE-ART

• The FRA used were produced in laboratory, in
• rder to control all properties.
• The effective water / cement ratio has been

corrected in order to include water to be absorbed by the FRA.

• 10, 30, 50 and 100% replacement ratios (%V)

were used.

• CEM I 42.5R cement, 2 natural CNA and 2 FNA were used.

EXPERIMENTAL PROGRAM DURABILITY TESTS (5 TESTS)

1. Immersion (28 and 120 d) 2. Capillarity (28 and 120 d) 3. Carbonation (28 and 120 d) 4. Chloride penetration (28 and 120 d) 5. Electrical resistivity (28 and 120 d)

Water bsorption by immersion Capilarity

• Water absorption by immersion

presented a linear increase with the replacement ratio. There was an increase of about 20% compared to the reference concrete, regardless of the test age.

• The higher porosity and the higher w/c

ratio are the main causes for this.

Absorção de água por imersão - Aim (%) Taxa de substituição - (%)

Absorção de água por imersão - Aim (%) Taxa de substituição - (%)

• Capillary water absorption increases

significantly with the replacement ratio.

• The sorptivity coefficients increase 185%

for 100% replacement ratio. Up to 50%, FRAC can still be considered of high quality.

Absorção capilar (kg/m2) Tempo - t (horas)

Absorção capilar (kg/m2) Tempo - t (horas)

POROSITY OF FRAC

Carbonation Chloride penetration

• Prof. de carbonatação - d (mm)

Tempo - t (dias)

• Prof. de carbonatação - d (mm)

Tempo - t (dias)

• Carbobation depth increase with the

replacement ratio, for any given age.

• Carbonation coefficient increases about

60% for C100R, compared to the reference concrete.

Coeficiente de difusão de cloretos - Dnssm (x10-12 m2/s) Taxa de substituição - r (%) 28 dias 120 dias

Coeficiente de difusão de cloretos - Dnssm (x10-12 m2/s) Taxa de substituição - r (%) 28 dias 120 dias

• Chloride penetration increases linearly

with the repacement ratio, with a maximum gain of 60%, for C100R.

• There is also a good correlation between

the chloride coefficient and the capillary water absorption, as well as with the porosuity measured through MIP .

Coeficiente de difusão de cloretos - Dnssm ( x 10-12 m2/s) Coeficiente de absorção capilar - S (x10-2 mm/min0.5)

Coeficiente de difusão de cloretos - Dnssm ( x 10-12 m2/s) Coeficiente de absorção capilar - S (x10-2 mm/min0.5)

POROSITY OF FRAC

Apresentação de resultados

Electrical resistivity

Resistividade eléctrica - m (.m) Taxa de substituição - r (%)

Resistividade eléctrica - m (.m) Taxa de substituição - r (%)

• The Electrical resistivity of concrete is

reduced with the presence of FRA, up to a maximum variation of 24%

• These results are directly inflenced by

the higher w/c ratio, and the higher porosity of the aggregates.

• It is possible os establish a good

correlation model between the electrical resistivity of FRAC and their chloride penetration resistance, allowing to determine the corrosion potencial faster.

Coeficiente de difusão de cloretos - Dnssm (x10-12 m2/s) Resistividade eléctrica - m (.m)

Coeficiente de difusão de cloretos - Dnssm (x10-12 m2/s) Resistividade eléctrica - m (.m)

Dnssm 51009. ρ

1,917

Dnssm 51009. ρ

1,917

POROSITY OF FRAC

C10R C30R C50R C100R

Immersion

= =

Capillarity Carbonatação Chloride penetration resistance

= =

Electrical resistivity

= =

Betão armado (Fmáx)

= = =

“=“ ≤ 10% 10%< “-” ≤ 30% 30% < “--” ≤ 60% “---” > 60%

CONCLUDING REMARKS

B10R B30R B50R B100R

Immersion

= =

• Capillarity
• Carbonatação

Chloride penetration resistance

= =

• Electrical resistivity

= =

• Betão armado (Fmáx)

= = =

• “=“ ≤ 10%

10%< “-” ≤ 30% 30% < “--” ≤ 60% “---” > 60%

CONCLUDING REMARKS

B10R B30R B50R B100R

Immersion

= =

• Capillarity
• Carbonatação
• Chloride penetration

resistance

= =

• Electrical resistivity

= =

• Betão armado (Fmáx)

= = =

• “=“ ≤ 10%

10%< “-” ≤ 30% 30% < “--” ≤ 60% “---” > 60%

CONCLUDING REMARKS

B10R B30R B50R B100R

Immersion

= =

• Capillarity
• Carbonatação
• Chloride penetration

resistance

= =

• Electrical resistivity

= =

• Betão armado (Fmáx)

= = =

• “=“ ≤ 10%

10%< “-” ≤ 30% 30% < “--” ≤ 60% “---” > 60%

+

CONCLUDING REMARKS

CONCLUDING REMARKS

The permeability properties for FRAC are clearly influenced by the presence and quantity of FRA. This is in direct relation with the inclusion of materials that are more porous and allow the transport of fluids through them.

• Water absorption by capillarity is influenced by the presence of FRA and by the

water/cement ratio; the age does not seem to affect the performance beyond 28 days;

• Capillary absorption is follows the same trend, even though the age effects are

noticeable;

• Carbonation resistance has a major decrease with the presence of FRA;
• Chloride penetration presents a good correlation with capillary absorption;
• Electrical resistivity can be established based on the chloride diffusion.